In power solutions of high performance CPU, switching converters with lower output voltage and higher output current are required. Multi-phase switching converters are widely used in these applications because of its good performance. For multi-phase switching converters, how to balance the output current of the plurality of switching circuits is a critical issue. Generally, the average output current of the switching circuits are compared with a reference value. Then the control signals of the switching circuits are adjusted based on the comparison result, so as to realize the current balance.
For prior digital controlled multi-phase switching converters, since the current resolution (minimum change of the average output current caused by the controlled parameter) is limited by the system clock frequency and the sampling rate of the analog digital converter, the current balance performance is not that good. FIG. 1 illustrates the current waveforms of the prior digital controlled multi-phase switching converters, wherein lave is the average output current of the switching circuit, Iref is the reference current, and Tad is the analog-digital sampling period of the average output current. As shown in FIG. 1, the average output current of the switching circuit is periodically changed around the reference current Iref. A high frequency ripple is formed and the current balance performance is poor.